Process for Introducing Fine and Coarse Additives for Hydroconversion of Heavy Hydrocarbons

ABSTRACT

A process for slurry-phase hydrocracking of a heavy hydrocarbon feedstock in a reactor, such as an upflow bubble column reactor, includes separately introducing additive in two size ranges into the feedstock. A fine size particle additive is introduced upstream of a coarse size particle additive.

BACKGROUND

1. Field of the Invention

The invention is related to a process for the thermal hydrogenationconversion of heavy hydrocarbon feedstocks.

2. Description of the Related Art

As the world's supply of crude oil becomes heavier and contains highersulfur levels, there is a challenge is to meet the growing demand forlight, high-quality, low-sulfur transportation fuels. The upgrading ofheavy hydrocarbon feedstocks may help to meet this demand. Severalprocesses are useful for upgrading heavy hydrocarbon feedstocks. Onesuch process is known as slurry phase hydrocracking. Slurry-phasehydrocracking converts any hydrogen and carbon containing feedstockderived from mineral oils, synthetic oils, coal, biological processes,and the like, hydrocarbon residues, such as vacuum residue (VR),atmospheric residue (AR), deasphalted bottoms, coal tar, and the like,in the presence of hydrogen under high temperatures and high pressures,for example, from about 750° F. (400° C.) up to about 930° F. (500° C.),and from about 1450 psig (10,000 kPa) up to about 4000 psig (27,500kPa), or higher. To prevent excessive coking during the reaction, finelypowdered additive particles made from carbon, iron salts, or othermaterials, may be added to the liquid feed. Inside the reactor, theliquid/powder mixture ideally behaves as a single homogenous phase dueto the small size of the additive particles. In practice, the reactormay be operated as an up-flow bubble column reactor or as a circulatingebulated bed reactor and the like with three phases due to the hydrogenmake up and light reaction products contributing to a gas phase, andlarger additive particles contributing to a solid phase, and the smalleradditive particles, feedstock and heavier reaction products contributingto the liquid phase, with the combination of additive and liquidcomprising the slurry. In slurry phase hydrocracking, feedstockconversion may exceed 90% into valuable converted products, and evenmore than 95% when a vacuum residue is the feedstock.

One example of slurry phase hydrocracking is known as VebaCombi-Cracking™ (VCC™) technology. This technology operates in a oncethrough mode where in one embodiment of the process, a proprietaryparticulate additive is added to a heavy feedstock, such as VR, to forma slurry feed. The slurry feed is charged with hydrogen and heated toreactive temperatures to crack the vacuum residue into lighter products.The vaporized conversion products may or may not be further hydrotreatedand/or hydrocracked in a second stage fixed bed catalyst reactor. Itproduces a wide range of distillate products including vacuum gas oil,middle distillate (such as diesel), naphtha and light gas.

It has been disclosed in various literature that the particulateadditive for slurry phase hydrocrackers may include a wide range ofmaterials. These materials reportedly include, but are not limited to,catalyst, red mud, iron (III) oxide, blast furnace dust, activated cokefrom hard coal or lignites, carbon black (soot), ashes from gasificationprocesses of crude oil, silicon oxides and other inorganic mineralscontaining iron, such as laterite or limonite. The particulate additivesare reported to have a wide particle size distribution between 0.1 and2,000 microns, with a preference towards to lower to middle of therange. It has been reported that it is desirable to include between 10and 40 wt % (weight percent) of the particles above 100 microns in size,with the balance of particles below 100 microns in size. To achievefiner control on the particle size distribution of the additiveintroduced into the process, a system has been proposed for introducinga fine particle size range and a coarse particle size range of additivesseparately into a mixing tank containing feed to obtain finer control onthe relative size distribution of the additives mixed in with thefeedstock. The slurry feedstock is then introduced into the highpressure pre-heat train with hydrogen and introduced into a reactor.See, e.g., U.S. Pat. No. 4,851,107, to Kretschmar et al. which isincorporated herein by reference.

Despite the various processes and alternatives available for upgradingheavy hydrocarbons, there is still a need for improving the existingprocesses to benefit the economics, efficiency and effectiveness of theunit operations.

SUMMARY

A process for slurry-phase hydrocracking of a heavy hydrocarbonfeedstock in a reactor, including an upflow bubble column reactorincludes separately introducing additive in two size ranges into thefeedstock. A fine size range particle additive is introduced in to theprocess upstream of a coarse size range particle additive. The processincludes introducing a first additive to the feedstock to form afines-loaded feedstock downstream of the feed charge pump. The finesadditive may include particles having a median particle sizedistribution from 20 to 500 microns and a surface area from 100 m²/g to800 m²/g. Separately, a second additive is introduced to thefines-loaded feedstock downstream of a feed charge pump and upstream ofor into the hydrocracking upflow bubble column reactor. The secondadditive may include coarse particles having a median particle size from400 to 2,000 microns. The reaction products are removed from thereactor, such as an upflow bubble column reactor, for furtherprocessing.

BRIEF DESCRIPTION OF THE DRAWINGS

The figure represents a simplified process flow diagram of a slurryphase hydrocracking process unit illustrating one embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In a slurry phase hydrocracking process with any reactor configurationincluding but not limited to an upflow bubble column reactor, one ormore additives may be introduced into the feedstock that results inseveral beneficial effects. Without being bound by any theory that isprovided for illustrative purposes in this description, it is believedthat an additive with high surface area, such as porous particles,allows the adsorption of asphaltene coke precursors formed during theexothermic thermal hydrocracking reaction of the feedstock. This allowsremoval of the coke precursors on the additive with the reactionproducts rather than allowing the coke precursors to deposit on theequipment internals, such as the exchangers and furnace in the preheattrain, and on the reactor internal surfaces. Preferably, for thisbeneficial effect, the additive particles exhibit a surface area greaterthan 100 meters-squared per gram (m²/g) or more preferably greater than200 m²/g.

In addition, it is believed that an additive with a sufficiently largeparticle size improves the hydrodynamics of the reactor, including butnot limited to an upflow bubble reactor. It is believed that the largeparticles assist in maintaining a turbulent backflow eddy recirculationin the reactor to achieve better mixing and more homogenous reactionkinetics. It is believe that the larger size additive particles alsoassist with the breakdown of foam that may form in the reactor, furtherimproving the reactor performance. Preferably, for this beneficialeffect in the reactor, the large additive particles have a medianparticle size between about 400 microns and 2000 microns. Thus, an idealadditive for all the beneficial effects noted would preferably have arelatively high surface area per weight, broad range of size and densityfor improved flow characteristics and reactor hydrodynamic performance.However, the particles should not be so large or dense that they settleout of the slurry feedstock flowing through the feed pre-heat train orthe reactor.

Rather than use one ideal additive, two additives with differentcharacteristics may be useful. The two additives are introduced atseparate points in the feed circuit to take advantage of the attributesof the particles, and minimize disadvantages that might accompanyintroducing all the additive with the initial feedstock charge. A firstadditive, referred to as “fines additive,” of a smaller median particlesize referred to as “fines particles,” or “fines additive particles,”that is highly porous with a high internal surface area is firstintroduced into the feedstock. The fines additive may be introducedeither in a feed mixing vessel, or it may be blended with a slurry oilthat may be a portion of the feedstock or any other liquid containingstream such as a high aromatic oil, such as light cycle oil, heavy cycleoil, or recycle heavy vacuum gas oil (VGO) from the VCC vacuum tower andthe like. The fines additive may be introduced into the main feedcircuit immediately upstream of the feed preheat train, either upstreamor downstream of the feed charge pump. The fines additive may beoptimized for adsorption of the asphaltene coke precursors generatedduring the heat up and hydrocracking reaction. It is believed that thesurface area of the fines additive particles is a key variable.

A second additive referred to as “coarse additive,” of a larger medianparticle size referred to as “coarse additive particles,” is thenintroduced into the fines-loaded feedstock at one or more locationsalong the feed preheat train. The feed preheat train may include one ormore feed heat exchangers, gas heat exchangers, feed-effluent heatexchangers and a feed preheat furnace upstream of the slurryhydrocracking reactor. The coarse additive may be introduced before,between or after the feed heat exchangers or gas heat exchangers, orfeed-effluent heat exchangers. The coarse additive may be introducedbefore or after the feed preheat furnace. The coarse additive may alsoor alternatively be introduced into the reactor inlet with thefines-loaded feedstock. Preferably, the coarse additive is introducedafter the feed preheat furnace. The coarse additive may be optimized forimproved hydrodynamic performance of the reactor and foam minimization.By introducing the coarse additive into or immediately upstream of thereactor, the lag time between adjustments to coarse additive injectionand reactor performance is reduced. Also, depending on the nature of thecoarse additive, such as density and hardness, by introducing the coarseadditive downstream of the preheat train equipment, additive particlessettling and equipment erosion may be avoided.

The fines additive particles may have a smaller particle size range thanthe coarse additive particles, and may have a lower, the same, or highersurface area per unit weight. The fines additive may preferably have aparticle size distribution between 20 microns and 500 microns. Belowthis size, it is believed that it may be difficult for the smallerparticles to be removed by a cyclone separator in the hot separator. Inone aspect, the maximum particle size limit is not critical but isbeneficial if controlled. There may be some overlap at the large sizerange of the fines additive with the small size range of the coarseadditives. However, if the first additive particles are too large it isbelieved that there may be settling of the particles in the feed preheattrain exchangers. Preferably, the fines additive may have a maximumparticle size nominally of 400 microns. That is to say, that the finesadditive may have been passed through a sieve to retain particlesgreater than 400 microns, but due to the irregular shapes of theindividual additive particles, it is possible that up to 5 wt % of thetotal particles passing through the 400 micron sieve may be larger than400 microns in one dimension. It is believed that particles as large as450 microns or 500 microns may possibly be passed by such a screeningoperation. Even up to 10 wt % of fine particles may be greater than 400microns, although, preferably, there is a cut-off at about 450 microns.If the large end of the particle size distribution of the fines additiveis too much, or too large, it is believed that this may cause problemsdue to the larger additive particles settling out in the feed preheatequipment, or causing erosion problems in the centrifugal feed pump andpossibly the heat exchangers. Preferably, the fines additives particlesare greater than 25 microns. More preferably the fines additiveparticles are greater than 50 microns. It is expected that the finesadditive particles may have a broad nominal size distribution betweenthe minimum and maximum sizes having either a short tail or a sharpcut-off at either end with a peak (or median particle size) at about 100microns, about 150 microns or about 200 microns, or preferably anywherebetween about 100 microns and about 200 microns.

The fine additive particles preferably have a porosity that provides asurface area sufficient to adsorb the coke pre-cursor asphaltenemolecules. It is believed that the fines additive particles should havesufficient porosity to provide an average surface area of at least 100m²/g, and preferably at least 200 m²/g, as previously reported foradditives in slurry phase hydrocracking processes.

The coarse additive particles may have a larger particle size rangecompared to the fines additive particles. The coarse additive particlesmay have a minimum size of 400 microns and a maximum size of 2,000microns. In one aspect, the minimum particle size limit is not criticalbut beneficial if controlled. There may be some overlap at the smallsize range with the large sizes of the fines additive. However, it isbelieved that the coarse additive if it is too small does not providethe beneficial hydrodynamic effects in the reactor. Therefore,additional energy is expended handling coarse additive particles thatare too small. Likewise, additive particles that are too large or tooheavy may settle in the reactor and not provide the beneficialhydrodynamic effects, which are believed to be directly related to thereactor dimensions. Therefore, it is preferred that the coarse additiveparticles have median particle size of about 800 microns for smallercommercial reactors (about 10,000 barrels per day of feed or smaller),about 1,200 microns for medium size commercial reactors (about 20,000barrels per day of feed), and about 1,600 microns or larger for largesize commercial reactors (about 30,000 barrels per day of feed orlarger). However, the actual optimal median particle size depends alsoon the reactor space velocity, coarse additive material properties(e.g., density), feedstock, pump handling limitations, and otheroperational variables.

The ratio of fines additive to coarse additive may be adjusted foroptimal operation. Preferably, the amount of coarse additive is between10 wt % and 40 wt % based on total weight of combined additiveintroduced into the process. More preferably, the amount of coarseparticles is between 15 wt % and 25 wt % of the combined additive. Evenmore preferably the amount of coarse particles is about 20 wt % of thecombined additive. The amount of coarse additive may fluctuate over timeas adjustments are made by operators to maintain a desired slurrydensity and pressure differential across the slurry reactor, includingan upflow bubble column reactor.

Preferably, the amount of fines additive is between 60 wt % and 90 wt %of the combined additive introduced to the process More preferably, theamount of fines particles is between 75 wt % and 85 wt % of the combineadditive. Even more preferably, the amount of fines particles is about80 wt % of the combined additive at steady state operations.

The fines additive may be introduced into the feedstock either via thefeed mixing tank or directly into the main feed line in an amount ofbetween about 0.1 wt % to 5 wt % of total feed. Preferably, less than2.5 wt % of fines additive is introduced. More preferably not more thanabout 2 wt % of fines additive is introduced to the feedstock.Preferably, not less than 0.1 wt % of fines additive is introduced. Whenintroduced directly into the main feed line, the fines additive ispre-mixed with a liquid, preferably an oil in a slurry drum to form anadditive slurry. The fines additive slurry may contain between 0.1 wt %and 60 wt % total solids in the mixing drum. Preferably, the finesadditive slurry contains from 10 wt % to 50 wt % total solids, and morepreferably from 30 wt % to 50 wt % total solids in the additive mixingdrum.

The coarse additive may be introduced into the feedstock either via thefeed mixing tank or directly into the process in an amount of from about0.05 wt % to 5 wt % of total feed. Preferably, less than 2.5 wt % ofcoarse additive is introduced. More preferably not more than about 2 wt% of coarse additive is introduced to the feedstock. Preferably, notless than 0.05 wt % of coarse additive is introduced. When introduceddirectly into the process, the coarse additive is pre-mixed with aliquid, preferably an oil in a slurry drum to form an additive slurry.The coarse additive slurry may contain between 0.1 wt % and 60 wt %total solids in the mixing drum. Preferably, the coarse additive slurrycontains from 10 wt % to 50 wt % total solids, and more preferably from30 wt % to 50 wt % of the total solids in the additive mixing drum.

Additives may be made of the following materials, some of which may beknown to those skilled in the art and have been described in theliterature relating to slurry phase hydrocracking. It has been disclosedthat the particulate additive for slurry phase hydrocrackers may includea wide range of materials. It is expected that these materials may bemodified to meet the above characteristics of the fines additive andcoarse additive. The material selected for the fines additive may be thesame or different than the material selected for the coarse additive.These materials reportedly include, but are not limited to,hydrotreating catalyst, spent catalysts, zeolites, red mud, iron (III)oxide, blast furnace dust, activated coke from hard coal or lignites,ashes from gasification processes and other inorganic mineralscontaining iron. Preferably, the fines additive particles are selectedfrom materials that include carbon. Preferably, the large particles havesome porosity to limit their apparent density to avoid settling of theparticles. Preferably, activated carbon-based materials such asactivated coal may be selected for both fines additives and coarseadditives.

The feedstock may be the following material: mineral and synthetic oil,heavy oils, residual oils, waste oils, shale oils, used oils, tar sandoils, coal oils such as oils derived from coal pyrolysis, coal tars suchas tars derived from coal liquifaction, vacuum residue, atmosphericresidue, deasphalted bottoms, comminuted coal, or other heavy oilsderived from any source, such as petroleum, and mixtures thereof, aswell as biomass derived materials, including lignin and pyrolysis oils.Lignin liquefies upon heating and up to 30 wt % may be blended with aheavy oil feedstock, such as vacuum residue. Preferably the feedstockmay include vacuum residue having a boiling temperature greater than500° C.

Referring to FIG. 1, a simplified hydrocracking process unit processflow diagram illustrates one embodiment of the invention. A vacuumresidue feedstock 10 is introduced into a slurry feed surge drum 12. Thefeedstock from the feed surge drum is taken by the feed pump 14 andintroduced into the high pressure feed circuit 16. The fines additive 18is introduced into the slurry mixing tank 20. This fines additivesslurry may include from 0.1% to 60% by weight additive, preferably 10 wt% to 50 wt % and more preferably about 30 wt % to 50 wt % additive, withthe balance being a slurry oil 22 or heavy oil carrier, such as vacuumresidue if such is used as the feedstock. The fines additive solids, isintroduced via a slurry pump 24 into the feedstock high pressure feedcircuit 16. Alternatively, the fines additive may be introduced upstreamof the feed pump 16 preferably in an amount less than 2 wt % of thefeedstock by weight, in which case due to the small particle size andlow solids concentrations, the feed pump 16 may be a centrifugal pump.The feedstock with the fines additive in the high pressure feed circuit16 is introduced to the feed preheat exchanger 26. The preheat exchanger26 may comprise one or more heat exchangers. For improved process heatefficiency, these preheat exchangers are feed-effluent exchangers,whereby heat is recovered from the 2^(nd) stage catalytichydroprocessing reactor effluent, the hot separator overhead effluent,or other high temperature energy sources from within or external to theprocess unit. Upstream of the preheat exchanger 26 the recycle gas 28and the makeup gas 30 are introduced into the high pressure feedcircuit. Hydrogen is introduced to the makeup gas compressor 32, andthen the high pressure make-up hydrogen 30 may be first introduced tothe recycle gas 28 to form a treat gas before being introduced into thehigh pressure feed circuit 16.

Another stream of additive material is made into slurry by mixing arange of coarse particle size additive 34 with a slurry oil 36, or heavyoil carrier, such as vacuum residue if such is used as the feedstock.The coarse additive slurry may include from 0.1% to 60% by weightadditive, preferably from 10 wt % to 50 wt % and more preferably fromabout 30 wt % to 50 wt % additive, with the balance being a slurry oilor heavy oil carrier, such as vacuum residue if such is used as thefeedstock. The percentage of coarse additive may vary depending on thesolids loading capability of the coarse additives pump 38, which may bea slurry-capable piston pump, though it is desirable to have as high assolids loading as practical. The coarse additives slurry may be added tothe fines-loaded feedstock via line 40 upstream of the preheat exchanger26. Alternatively, the coarse additives slurry may be added via line 42after the preheat exchanger 26 and upstream of the furnace 46, or vialine 44 after the furnace directly to the inlet to the first stage gasphase reactor 48, or directly into the reactor 48. The coarse additivesslurry may be introduced at any place along the feed preheat train.Because the feed preheat train includes several exchangers and afurnace, there are multiple locations where the coarse additive slurrymay be introduced. Because coke precursors are formed as soon as thevacuum residue begins heating up, it may be desirable to introduce thecourse additives slurry upstream of the preheat train. Alternatively, tominimize erosion of the exchanger and heat exchanger or furnace theequipment that may be desirable to introduce the course additives slurryat a later point and rely upon the fines additives to adsorb the cokeprecursors formed upstream of the coarse additive injection point.

The effluent stream 50 from the slurry phase reactor 48 is introducedinto a hot separator 52. The reaction products 54 are removed from thetop of the hot separator 52 and introduced into the second stage reactor56, such as a second stage catalytic hydroprocessing reactor, forfurther processing, such as hydrotreating and/or hydrocracking. Thebottoms 58 from the hot separator, which may be primarily unconvertedresidue are introduced into a vacuum column 60. The overhead productstream of the vacuum column is introduced into a pump 62 and then fed tothe second stage reactor 56. The vacuum column bottom stream 64 may be aheavy vacuum residue that may be recycled into the feedstock of thisunit, or may be used for other products, such as pitch or asphalt. Theeffluent 66 from the second stage reactor is introduced into the coldseparator 68. The hydrogen, off gases, sulfur and other gases, arerecovered from the top of the cold separator through line 70 andintroduced to a gas cleaning unit 72. Off gases, sulfur compounds andother undesirable components may be removed through line 74 and sent forfurther processing or disposal. The hydrogen and other light gas is sentas recycle gas through line 76 to the recycle gas compressor 78 andrecycled back into the feedstock.

The bottoms stream 80 from the cold separator 68 is sent to afractionator column 82. In the fractionator column 82, a variety ofproduct fractions may be removed such as propane and other like gasesthrough line 84, naphtha through line 86, a middle distillate cutthrough line 88, and a vacuum gas oil line 90 from the bottom of thefractionator column.

The process may be modified with different additives optimized fordifferent feedstocks with a finer level of control because of theseparate additive feed control systems, and the reduced lag time byinjecting the coarse additive directly into the reactor or closerupstream to the reactor compared to where the fines additive isintroduced. Because additive of a larger particle size may be tooerosive for use with a centrifugal pump, embodiments of the inventionmay also provide the advantage that a centrifugal pump may be used forfines-loaded feedstock, and a smaller piston pump for the coarseadditive slurry. This is economically advantageous compared to a singlelarge feed piston pump when the mixing feed tank has a single broadparticle size additive used encompassing both the fines and coarseparticle size distribution.

One of ordinary skill in the art may appreciate other advantages andmodifications of the above described embodiments based on the teachingsherein. However, the above embodiments are for illustrative purposesonly. The invention is defined not by the above description but by theclaims appended hereto.

What is claimed is:
 1. A process for slurry-phase hydrocracking of aheavy hydrocarbon feedstock in a slurry phase hydrocracking reactor, theprocess comprising: introducing a first additive to the feedstockupstream of a pre-heat exchanger to form a fines-loaded feedstock, theadditive comprising fines particles having a particle size distributionless than 500 microns, separately introducing a second additive to thefines-loaded feedstock downstream of a feed charge pump and upstream ofthe slurry phase hydrocracking reactor, the second additive comprisingcoarse particles having a median particle size between 400 microns and2,000 microns; and removing reaction products from the slurry phasehydrocracking reactor.
 2. The process of claim 1, wherein the slurryphase hydrocracking reactor is an upflow bubble column reactor.
 3. Theprocess of claim 1, wherein the slurry phase hydrocracking reactor is acirculating ebulated bed reactor.
 4. The process of claim 1, wherein theheavy hydrocarbon feedstock comprises of a mineral oil, synthetic oil,heavy oil, residual oil, waste oil, shale oil, used oil, tar sand oil,coal oil, coal tar, vacuum residue, atmospheric residue, deasphaltedbottoms, comminuted coal, biomass-derived materials, and mixturesthereof.
 5. The process of claim 1, wherein the heavy hydrocarbonfeedstock comprises vacuum residue.
 6. The process of claim 1, whereinthe first additive is introduced to the feedstock in a feed mixingvessel.
 7. The process of claim 1, wherein the first additive isintroduced to the feedstock downstream of the feed charge pump.
 8. Theprocess of claim 1, wherein the second additive is introduced to thefines-loaded feedstock immediately upstream of a heat exchanger in afeed preheat train.
 9. The process of claim 1, wherein the secondadditive is introduced to the fines-loaded feedstock immediatelyupstream of a feed furnace in a feed preheat train.
 10. The process ofclaim 1, wherein the second additive is introduced immediately upstreamof the slurry phase hydrocracking reactor.
 11. The process of claim 1,wherein the second additive is introduced at a feed inlet of the slurryphase hydrocracking reactor.
 12. The process of claim 1, wherein thesecond additive is introduced at a feed inlet of a second or subsequentslurry phase hydrocracking reactor when multiple reactors in series areemployed.
 13. The process of claim 1, wherein the first additivecomprises 0.1-5 wt % of said fines-loaded feedstock.
 14. The process ofclaim 1, wherein the first additive comprises less than 2.5 wt % of saidfines-loaded feedstock.
 15. The process of claim 1, wherein the firstadditive comprises less than 1 wt % of said fines-loaded feedstock. 16.The process of claim 1, wherein the first additive comprises a particlesize distribution between 20 microns to 450 microns.
 17. The process ofclaim 1, wherein the first additive comprises a particle distributionbetween 50 microns and 400 microns.
 18. The process of claim 1, whereinthe first additive comprises a median particle size of between 100microns and 200 microns.
 19. The process of claim 1, wherein the firstadditive comprises activated carbon.
 20. The process of claim 1, whereinthe first additive comprises of modified activated carbon.
 21. Theprocess of claim 1, wherein the second additive comprises activatedcarbon.
 22. The process of claim 1, wherein the second additivecomprises modified activated carbon.
 23. The process of claim 1, whereinthe first additive comprises of one or more of hydrotreating catalyst,spent catalyst, red mud, iron (III) oxide, blast furnace dust, activatedcoke from hard coal or lignites, carbon black (soot), ashes fromgasification processes of crude oil, silicon oxides and other inorganicminerals and mixtures thereof.
 24. The process of claim 1, wherein thesecond additive comprises of one or more of hydrotreating catalyst,spent catalyst, red mud, iron (III) oxide, blast furnace dust, activatedcoke from hard coal or lignites, carbon black (soot), ashes fromgasification processes of crude oil, silicon oxides and other inorganicminerals and mixtures thereof.
 25. The process of claim 1, wherein thesecond additive comprises a median particle size between 800 microns and1,200 microns.
 26. The process of claim 1, wherein the first additivecomprises between 60 wt % and 90 wt % of total first and secondadditives.
 27. The process of claim 1 wherein the heavy oil feedstockcomprises a vacuum residue and between 1 wt % and 30 wt % lignin.